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Show 328 THE NATIONAL GEOGRAPHIC MAGAZINE secutive years, a n d o t h er caves have yielded comparable amounts. A good productive bat cave has the advantage over a gold mine in being self-perpetuating. But the real value of the bats lies in their enormous destruction of insect pests, which is well illustrated by a permanent yield of 60 tons a year of insect shells in one locality. THE LONG-EARED BAT STUDIED DURING HIBERNATION Besides the vast numbers of Free-tailed, or Guano, Bats, which hang close together under the roof of the highest room in Carlsbad Cavern and by their rank odor apparently keep other bats at a distance, there are about a dozen species that occupy, or have occupied, various parts of the cave or near-by caves and canyons. Of the 18 species of bats known in New Mexico, 13 have been found in this vicinity. In the farthest, deepest room of the cave, where there were no living bats, numerous skeletons were found lying on the dusty floor. They were usually old and bleached, but some were dried mummies that may have been there for many years. Most of these were of the Guano Bats, but they included also bones of manv other species. The Long-eared Bats, Cory-norhinus rafinesquii pallcscens, one of the most interesting and spectacular species of the region, were found in considerable numbers in McKitterick Cave, some 20 miles farther north. On April 15, when first discovered, they were still in profound winter sleep, hanging head down from the low limestone ceiling and on the rock walls of the cool, dry rooms, their great ears rolled up in spiral coils like rams' horns on each side of the head. |